U.S. patent application number 14/961138 was filed with the patent office on 2016-06-16 for focus detection apparatus and control method for focus detection apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Hirohito Kai.
Application Number | 20160173758 14/961138 |
Document ID | / |
Family ID | 56112409 |
Filed Date | 2016-06-16 |
United States Patent
Application |
20160173758 |
Kind Code |
A1 |
Kai; Hirohito |
June 16, 2016 |
FOCUS DETECTION APPARATUS AND CONTROL METHOD FOR FOCUS DETECTION
APPARATUS
Abstract
A focus detection apparatus includes a focus detection unit
configured to detect a focus state in each of a plurality of focus
detection regions, an acquisition unit configured to acquire an
adjustment value used for adjustment of a detection result, for
each of the focus detection regions, and a control unit configured
to switch between a first mode and a second mode based on focus
states detected in the focus detection regions. In the first mode,
the acquisition unit acquires the adjustment values for the focus
detection regions, based on a focus state in a specific first focus
detection region. In the second mode, the acquisition unit acquires
the adjustment value for each of the focus detection regions, based
on a focus state detected in each of the focus detection
regions.
Inventors: |
Kai; Hirohito; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
56112409 |
Appl. No.: |
14/961138 |
Filed: |
December 7, 2015 |
Current U.S.
Class: |
348/345 |
Current CPC
Class: |
H04N 5/23212 20130101;
H04N 5/232122 20180801; H04N 5/232933 20180801; H04N 5/23245
20130101; H04N 5/232127 20180801 |
International
Class: |
H04N 5/232 20060101
H04N005/232 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 2014 |
JP |
2014-249677 |
Claims
1. A focus detection apparatus comprising: a focus detection unit
configured to detect a focus state in each of a plurality of focus
detection regions; an acquisition unit configured to acquire an
adjustment value used for adjustment of a detection result obtained
by the focus detection unit, for each of the plurality of focus
detection regions; and a control unit configured to switch between
a first mode and a second mode based on focus states detected in
the plurality of focus detection regions, wherein, in the first
mode, the acquisition unit acquires the adjustment values for the
plurality of focus detection regions, based on a focus state
detected by the focus detection unit in a specific first focus
detection region, and wherein, in the second mode, the acquisition
unit acquires the adjustment value for each of the plurality of
focus detection regions, based on a focus state detected by the
focus detection unit in each of the plurality of focus detection
regions.
2. The focus detection apparatus according to claim 1, wherein the
focus detection unit detects a defocus amount in each of the
plurality of focus detection regions, and wherein, in a case where
each of defocus amounts in the plurality of focus detection regions
is within a threshold, the control unit switches to the second mode
and the acquisition unit acquires the adjustment value in the
second mode.
3. The focus detection apparatus according to claim 2, wherein, in
a case where at least one of the defocus amounts in the plurality
of focus detection regions is beyond the threshold, the control
unit switches to the first mode and the acquisition unit acquires
the adjustment value in the first mode.
4. The focus detection apparatus according to claim 1, further
comprising a determination unit configured to determine whether an
object is a plane, wherein the control unit is configured to switch
between the first mode and the second mode based on a result of
determination by the determination unit.
5. The focus detection apparatus according to claim 4, wherein, in
a case where an object is determined to be a plane by the
determination unit, the control unit switches to the second mode
and the acquisition unit acquires the adjustment value in the
second mode, and wherein, in a case where an object is determined
not to be a plane by the determination unit, the control unit
switches to the first mode and the acquisition unit acquires the
adjustment value in the first mode.
6. The focus detection apparatus according to claim 1, wherein, in
the second mode, the acquisition unit acquires the adjustment value
in a manner such that focus states in the plurality of focus
detection regions after adjustment become identical.
7. The focus detection apparatus according to claim 1, further
comprising: an imaging unit configured to capture an image; and a
lens control unit configured to control a position of a focus lens,
wherein the lens control unit performs control to move the focus
lens to a plurality of different positions, and, at each of the
positions, the imaging unit captures an image and the focus
detection unit detects a focus state, and wherein the acquisition
unit acquires the adjustment value, based on a focus state
corresponding to an image selected from captured images.
8. The focus detection apparatus according to claim 7, further
comprising a region detection unit configured to detect an image
region used for determination in selecting the image from the
captured images, wherein the first focus detection region is
selected according to the image region detected by the region
detection unit.
9. The focus detection apparatus according to claim 8, wherein the
first focus detection region is selected from focus detection
regions each being at least partially included in the image region
detected by the region detection unit.
10. The focus detection apparatus according to claim 8, wherein a
focus detection region closest to a center of the image region
detected by the region detection unit is selected as the first
focus detection region.
11. The focus detection apparatus according to claim 8, further
comprising a display unit capable of enlarging and displaying a
captured image, wherein the region detection unit detects an
enlarged image region displayed by the display unit, when the image
is selected from the captured images.
12. A control method for a focus detection apparatus, the method
comprising: detecting a focus state in each of a plurality of focus
detection regions; acquiring the adjustment value used for
adjustment of a detection result obtained by the detecting, for
each of the plurality of focus detection regions; controlling
switching between a first mode and a second mode of the focus
detection apparatus based on focus states detected in the plurality
of focus detection regions, wherein, in the first mode, the
acquiring acquires the adjustment values for the plurality of focus
detection regions, based on a focus state detected by the detecting
in a specific first focus detection region, and wherein, in the
second mode, the acquiring acquires the adjustment value for each
of the plurality of focus detection regions, based on a focus state
detected by the detecting in each of the plurality of focus
detection regions.
13. The control method according to claim 12, wherein the detecting
a focus state includes detecting a defocus amount in each of the
plurality of focus detection regions, and wherein, in a case where
each of defocus amounts in the plurality of focus detection regions
is within a threshold, the controlling includes switching to the
second mode and the acquiring includes acquiring the adjustment
value in the second mode.
14. The control method according to claim 13, wherein, in a case
where at least one of the defocus amounts in the plurality of focus
detection regions is beyond the threshold, the controlling includes
switching to the first mode and the acquiring includes acquiring
the adjustment value in the first mode.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to an imaging
apparatus, and in particular it relates to a focus detection
apparatus having a plurality of focus detection regions suitable
for an imaging apparatus, such as a photographing camera.
[0003] 2. Description of the Related Art
[0004] In many cases, a single-lens reflex (SLR) camera is equipped
with a focus detection system employing a phase difference
detection method. The phase difference detection method detects a
focus state (a defocus amount) of a shooting optical system
provided in an interchangeable lens, based on a phase difference
between a pair of images formed by light passing through the
shooting optical system. In the phase difference detection method,
an in-focus position may not be accurately detected due to, for
example, environmental influence during shooting, or influence of
manufacturing errors of the single-lens reflex camera and the
interchangeable lens.
[0005] To address such inaccuracies, Japanese Patent Application
Laid-Open No. 2005-227639 discusses an imaging apparatus having a
function of allowing a user to arbitrarily make a fine adjustment
to an adjustment value of an automatic focusing (AF) function
(i.e., AF microadjustment). However, according to the apparatus
discussed in Japanese Patent Application Laid-Open No. 2005-227639,
the user is required to manually repeat work for shooting and check
to confirm whether a result of the fine adjustment made by the user
is appropriate.
[0006] In connection the user's burden, a method for setting an
adjustment value with simpler work has been discussed. Japanese
Patent Application Laid-Open No. 2005-109621 discusses an imaging
apparatus that captures images with different focus states
(performs a focus bracket shooting), and calculates an AF
correction amount (an adjustment value) based on a focus position
displacement amount associated with an image selected by a user
from the captured images.
[0007] In Japanese Patent Application Laid-Open No. 2005-109621,
the captured image includes an error in a focus-state detection
result (a distance measurement result) and an error in driving for
a focus position shift amount, and thus the calculated AF
correction amount may not be appropriate. In addition, in Japanese
Patent Application Laid-Open No. 2005-109621, to set the AF
correction amount for all distance measurement points (focus
detection regions), it is necessary to calculate the AF correction
amount by performing the focus bracket shooting for each of the
distance measurement points. Therefore, as the number of distance
measurement points increases, more work is necessary.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to a focus detection
apparatus and a control method for the focus detection apparatus,
which are capable of making a highly accurate adjustment of a value
of an AF function with simple operation, even if there is a
plurality of focus detection regions to be used for adjustment of a
focus detection result.
[0009] According to an aspect of the present invention, a focus
detection apparatus includes a focus detection unit configured to
detect a focus state in each of a plurality of focus detection
regions, an acquisition unit configured to acquire an adjustment
value used for adjustment of a detection result obtained by the
focus detection unit, for each of the plurality of focus detection
regions, and a control unit configured to switch between a first
mode and a second mode based on focus states detected in the
plurality of focus detection regions, wherein, in the first mode,
the acquisition unit acquires the adjustment values for the
plurality of focus detection regions, based on a focus state
detected by the focus detection unit in a specific first focus
detection region, and wherein, in the second mode, the acquisition
unit acquires the adjustment value for each of the plurality of
focus detection regions, based on a focus state detected by the
focus detection unit in each of the plurality of focus detection
regions.
[0010] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagram illustrating a schematic configuration
of an imaging apparatus according to an exemplary embodiment.
[0012] FIG. 2 is a flowchart illustrating automatic focusing (AF)
fine adjustment processing according to the present exemplary
embodiment.
[0013] FIG. 3 is a diagram illustrating an example of an
adjustment-value setting screen according to the present exemplary
embodiment.
[0014] FIG. 4 is a diagram illustrating an example of a screen for
displaying a stored AF adjustment value according to the present
exemplary embodiment.
[0015] FIG. 5 is a flowchart illustrating processing in a second
adjustment mode according to the present exemplary embodiment.
[0016] FIGS. 6A, 6B, and 6C are diagrams illustrating examples of a
focus detection result obtained in the second adjustment mode
according to the present exemplary embodiment.
[0017] FIGS. 7A and 7B are diagrams each illustrating an example of
an AF adjustment value determined in the second adjustment mode
according to the present exemplary embodiment.
[0018] FIG. 8 is a flowchart illustrating processing for
determining the AF adjustment value in the second adjustment mode
according to the present exemplary embodiment.
DESCRIPTION OF THE EMBODIMENTS
[0019] An exemplary embodiment will be described below with
reference to the drawings.
[0020] FIG. 1 is a schematic diagram of an imaging apparatus
including a focus detection apparatus according to the present
exemplary embodiment. In FIG. 1, a lens unit 100 is detachably
attached to a front face of a camera body 200. The camera body 200
and the lens unit 100 are electrically connected via mount contacts
104.
[0021] First, a configuration of the lens unit 100 will be
described. A shooting lens 101 includes a focus lens for focus
adjustment. In FIG. 1, the shooting lens 101 is illustrated as a
single lens, but may be a group of lenses.
[0022] Further, the shooting lens 101 may include a zoom lens for
magnification and a fixed lens. An iris diaphragm 105 adjusts the
quantity of light entering the camera body 200. The shooting lens
101 and the iris diaphragm 105 form a shooting optical system.
[0023] A lens control unit 103 performs data communication with the
camera body 200 via the mount contacts 104, and controls the
position of the shooting lens 101 by controlling a lens drive
source 102 based on an instruction from the camera body 200. The
lens drive source 102 is provided to move the shooting lens 101,
and is configured using a stepping motor and associated circuitry,
or like hardware and control logic.
[0024] Next, a configuration of the camera body 200 will be
described. An imaging sensor 209 (an imaging unit) is configured
using a charge coupled device (CCD) sensor, a complementary metal
oxide semiconductor (CMOS) sensor, or the like. The imaging sensor
209 photoelectrically converts an object image formed by a light
beam passing through the shooting optical system into an electrical
signal, thereby outputting an image pickup signal. A shutter 208
regulates the quantity of light entering the imaging sensor
209.
[0025] A main mirror 201 has a semitransparent section. The main
mirror 201 is retracted (moved) out of an optical path of an
imaging light beam during shooting, and positioned obliquely in the
imaging light beam (in the optical path) during focus detection.
FIG. 1 illustrates a (mirror down) state where the main mirror 201
is inserted into the path of imaging light beam. Further, in a
state of being obliquely positioned in the imaging light beam, the
main mirror 201 guides a part of the light beam passing through the
shooting optical system, to a finder optical system. The finder
optical system includes a focusing screen 203, a pentaprism 204,
and an eyepiece lens 205. In addition, the light beam reflected by
the main mirror 201 enters a photometry unit (not shown), so that a
luminance signal and a chrominance signal of an object optical
image passing through the shooting optical system are detected.
[0026] A sub-mirror 202 is foldable and expandable with respect to
the main mirror 201, in synchronization with movement of the main
mirror 201. A part of the light beam passes through a
semitransparent section of the main mirror 201, and then reflects
off the sub-mirror 202 to go downward (in the figure). This part of
the light beam then enters a focus detection unit 207 employing a
phase difference system, so that a focus state of the focus lens is
detected. The focus detection unit 207 includes a photoelectric
conversion element (a pair of line sensors). A defocus amount is
detected, based on a phase difference between image signals
resulting from photoelectric conversion by the pair of line sensors
that correspond to a focus detection region.
[0027] A system control unit 210 controlling the entire camera body
200 includes a central processing unit (CPU), and a random access
memory (RAM) serving as a storage device. The system control unit
210 performs data communication with the lens control unit 103 via
the mount contacts 104, thereby transmitting an instruction for
driving the shooting lens 101 and receiving a status of driving the
shooting lens 101.
[0028] A display unit 212 serves as a display, such as a liquid
crystal display (LCD) or an OLED display, and displays shooting
information and a captured image so that a user can confirm them.
The system control unit 210 controls display by the display unit
212.
[0029] An operation unit 213 is connected to the system control
unit 210, and includes operation members for operating the camera
body 200, such as a power switch to power on/off the camera body
200, and a release button. When any of these operation members is
operated, a signal is input into the system control unit 210
according to the pertinent operation. Connected to the release
button or the operation unit 213 are a release switch SW1 to be
turned on by a first stroke operation (half-pressing operation),
and a release switch SW2 to be turned on by a second stroke
operation (full-pressing operation), performed on the release
button by the user.
[0030] A counter 214 is connected to the system control unit 210,
and counts the number of shooting times when a focus bracket
shooting is performed. The system control unit 210 resets the count
value of the counter 214 when necessary.
[0031] A storage unit 211 such as an electrically erasable
programmable ROM (EEPROM) stores identification (ID) information
unique to the camera body 200. The storage unit 211 also stores
adjustment values of parameters for shooting, which are obtained by
adjustment using a reference lens (a shooting lens used in factory
adjustment of the specific camera body). The system control unit
210 controls storage and reading processing for the storage unit
211 such as the EEPROM.
[0032] Meanwhile, the lens unit 100 includes a memory (not
illustrated) for storing performance information of the lens unit
100 such as a focal length and a full aperture vale, and lens ID
information that is unique information for identifying the lens
unit 100. This lens memory also stores information received from
the system control unit 210 by communication. The performance
information and the lens ID information are transmitted from the
lens control unit 103 to the system control unit 210, by initial
communication when the lens unit 100 is attached to the camera body
200. The system control unit 210 stores these received pieces of
information, into the storage unit 211.
[0033] FIG. 2 is a flowchart illustrating automatic focusing (AF)
fine adjustment processing according to the present exemplary
embodiment. In the present exemplary embodiment, the user can
select either a first adjustment mode for performing AF
microadjustment for arbitrarily setting an AF adjustment value, or
a second adjustment mode for determining an AF adjustment value by
using a micro adjustment support (MAS). The first adjustment mode
and the second adjustment mode will be described in detail below.
The present exemplary embodiment is also applicable to an imaging
apparatus having only the second adjustment mode.
[0034] First, after the lens unit 100 and the camera body 200 are
in an operational state (e.g., in an imaging state), in step S201,
the system control unit 210 determines whether the first adjustment
mode is selected. If the first adjustment mode is selected (Yes in
step S201), the processing proceeds to step S205. If the second
adjustment mode is selected (No in step S201), the processing
proceeds to step 202. In step 205, the system control unit 210
controls the display unit 212 to display an adjustment-value
setting screen for performing the AF microadjustment. FIG. 3 is a
diagram illustrating an example of the adjustment-value setting
screen.
[0035] The AF microadjustment is a process in which the user
directly sets an AF adjustment value, by determining an amount and
a direction of defocus between an in-focus position based on a
defocus amount detected by the focus detection unit 207 and an
actual in-focus position, based on an image taken by the user. As
illustrated in FIG. 3, in the AF microadjustment according to the
present exemplary embodiment, the user can arbitrarily set the AF
adjustment value in steps of one scale unit within a range of a
scale of .+-.20, so that the in-focus position based on the defocus
amount can be shifted by the set AF adjustment value. In the
present exemplary embodiment, a focus adjustment amount per scale
unit of the AF adjustment value is a constant multiple of F.delta.
(where F is an open F-number of the shooting lens, and .delta. is a
permissible confusion circle diameter) representing a depth. In
FIG. 3, "0" is a factory-set reference position of the imaging
apparatus. In the adjustment-value setting screen illustrated in
FIG. 3, a black triangle pointer indicates the AF adjustment value
stored in the storage unit 211. The user can change the AF
adjustment value, by performing an operation to move the black
triangle pointer along the scale. When the adjustment-value setting
screen is displayed, the processing proceeds to step S206.
[0036] In step S206, the system control unit 210 determines whether
operation to change the AF adjustment value is performed by the
user in the adjustment-value setting screen. If the operation to
change the AF adjustment value is performed (Yes in step S206), the
processing proceeds to step S207. If the operation to change the AF
adjustment value is not performed (No in step S206), the processing
proceeds to step S208.
[0037] In step S207, the system control unit 210 controls the
display unit 212 to update the display of the adjustment-value
setting screen, according to the operation of the user. Here, in
the adjustment-value setting screen illustrated in FIG. 3, the
black triangle pointer indicates a position corresponding to the
operation of the user.
[0038] In step S208, the system control unit 210 determines whether
the AF adjustment value is determined by the user. Here, the system
control unit 210 determines whether a "SET" button is selected in
the adjustment-value setting screen illustrated in FIG. 3. If the
"SET" button is not selected (No in step S208), the processing
returns to step S206 to repeat the process described above. On the
other hand, if the "SET" button is selected (Yes in step S208), the
processing proceeds to step S209 where the display of the
adjustment-value setting screen is terminated, and then the
processing proceeds to step S210.
[0039] In step S210, the system control unit 210 determines whether
there is a difference between the AF adjustment value stored in the
storage unit 211 when the first adjustment mode is selected, and
the AF adjustment value newly set in steps S206 to S208. If there
is a difference (Yes in step S210), the processing proceeds to step
S204 to update the AF adjustment value. If there is no difference
(No in step S210), the AF fine adjustment processing
terminates.
[0040] FIG. 4 is a diagram illustrating a screen for displaying the
AF adjustment value stored in the storage unit 211. This scale is
common to the first adjustment mode and the second adjustment mode.
In the first adjustment mode, the user can change the AF adjustment
value acquired in the second adjustment mode. In FIG. 4, a white
triangle pointer indicates the AF adjustment value previously
stored, whereas the black triangle pointer indicates the AF
adjustment value to be stored newly. As for display in a case where
the AF adjustment value can be set in each of a plurality of focus
detection regions, it is conceivable that, for example, the user
may be allowed to select a desired focus detection region, and an
AF adjustment value corresponding to the selected focus detection
region may be displayed. Displaying a screen as illustrated in FIG.
4 enables the user to confirm what AF adjustment value is
stored.
[0041] On the other hand, if the second adjustment mode is selected
in step S201 (No in step S201), then in step S202, an AF adjustment
value is calculated in the second adjustment mode. In the second
adjustment mode, while the focus lens is driven so that the
position of the focus lens moves on a predetermined amount basis, a
plurality of images are captured and defocus amounts are detected
by the focus detection unit 207. Based on the defocus amount
corresponding to an image selected by the user from among the
captured images, the AF adjustment value is calculated. The
processing performed in step S202 will be described in detail
below. When the AF adjustment value is calculated, the processing
proceeds to step S203.
[0042] In step S203, the system control unit 210 determines whether
to update the AF adjustment value stored in the storage unit 211,
to the AF adjustment value calculated in step S202. Here, for
example, if the AF adjustment value is to be updated (Yes in step
S203), specifically, for example, when setting of the calculated AF
adjustment value is selected by predetermined operation, the
processing proceeds to step S204. If the AF adjustment value is not
to be updated (No in step S203), processing for setting the AF
adjustment value terminates.
[0043] In step S204, the system control unit 210 updates the AF
adjustment value by storing the AF adjustment value acquired in
step S202 or acquired in steps S206 to step S210, into the storage
unit 211. The processing for setting the AF adjustment value then
terminates.
[0044] The AF adjustment value thus stored in the storage unit 211
is used for correction of the defocus amount that is detected by
the focus detection unit 207 during actual shooting (during
capturing of a recorded image) using the following expression
(1).
Defocus amount to be used for AF control=detected defocus
amount+adjustment value+AF adjustment value (1)
[0045] In addition, in the above-described expression (1),
"adjustment value" represents defocus-amount adjustment data in
manufacturing. Based on "defocus amount to be used for AF control"
corrected using the above-described expression (1), the system
control unit 210 transmits an instruction for driving the focus
lens, to the lens control unit 103. Here, when there is a plurality
of focus detection regions, the focus detection region to be used
for AF control may be a central focus detection region that is
generally regarded as achieving high accuracy. Alternatively, the
focus detection region to be used for AF control may be arbitrarily
selected by the user, or may be automatically selected by the
imaging apparatus depending on an object.
[0046] Next, the processing for setting the AF adjustment value in
the second adjustment mode performed in step S202 will be described
with reference to a flowchart of FIG. 5.
[0047] First, in step S501, the system control unit 210 controls
the display unit 212 to display a screen for focus bracket shooting
adjustment. Examples of information to be displayed include an
operation instruction for the user. When the screen for focus
bracket shooting adjustment is displayed, the processing proceeds
to step S502.
[0048] In step S502, the focus detection unit 207 detects a defocus
amount. The focus detection region targeted for the detection of
the defocus amount may be a central focus detection region, a
region arbitrarily selected by the user, or a region automatically
selected by the imaging apparatus depending on an object. When the
defocus amount is detected, the processing proceeds to step S503.
In step S503, the system control unit 210 transmits an instruction
for driving the focus lens based on the detected defocus amount, to
the lens control unit 103. When driving of the focus lens to a lens
position corresponding to the defocus amount is completed, the
processing proceeds to step S504.
[0049] In step S504, the system control unit 210 determines whether
the object used for the detection of the defocus amount in step
S502 is appropriate for the calculation of the AF adjustment value.
Here, for example, an AF reliability evaluation value is calculated
based on an image signal (a signal generated by photoelectrically
converting light received by the above-described pair of line
sensors) used for the detection of the defocus amount. When an
object is dark or when contrast is low, focus detection accuracy of
the focus detection unit 207 may decrease. In such a case, i.e.,
when the focus detection accuracy decreases, the AF reliability
evaluation value is calculated to be low. The system control unit
210 determines whether the object is an appropriate object, based
on the calculated AF reliability evaluation value. If the object is
an appropriate object (Yes in step S504), the processing proceeds
to step S505. If the object is not an appropriate object (No in
step S504), the processing proceeds to step S517.
[0050] The AF reliability evaluation value may be calculated from a
plurality of viewpoints, so that a plurality of values (such as
luminance of the object and contrast of the object, as described
above) may be used. In this case, in step S504, the determination
may be made based on whether all the AF reliability evaluation
values are satisfied, or based on the value from a predetermined
viewpoint.
[0051] If the object is not an appropriate object (No in step
S504), then in step S517, the system control unit 210 controls the
display unit 212 to display an error message. Conceivable examples
of the content of the error message include information indicating
the occurrence of an error, and information indicating a probable
cause of an error. When display of the error message is completed,
the processing proceeds to step S518, to receive an instruction for
redoing or cancelling the adjustment by the user. If the adjustment
is to be redone (Yes in step S518), the processing returns to step
S502. If the adjustment is to be cancelled (No in step S518), the
processing proceeds to step S516.
[0052] On the other hand, in step S505, the system control unit 210
transmits a driving instruction to the lens control unit 103 so
that the focus lens moves to a focus bracket shooting start
position. When a bracket interval for capturing each image is "s"
and the number of captured images (a captured-image count) is "m",
the focus bracket shooting start position is closer to a closest
distance side by (m-1).times.s/2, from the in-focus position
detected in step S502.
[0053] In step S506, the system control unit 210 resets a counter
value n of the counter 214. This counter value n is associated with
the number of captured images of the focus bracket shooting, and is
set to "0" before start of the focus bracket shooting. The
processing then proceeds to step S507.
[0054] In step S507, the focus detection unit 207 detects a defocus
amount. Here, the defocus amount is detected for each of focus
detection regions for which the AF adjustment value is to be set.
The defocus amount may be detected for a plurality of times in each
of the focus detection regions, and an average value of the
detected defocus amounts may be used as a detection result for each
of the focus detection regions. The detected defocus amount is
eventually stored in an internal memory, in association with an
image to be captured in step S509. When detection of the defocus
amount is completed, the processing proceeds to step S508.
[0055] In step S508, the system control unit 210 moves the main
mirror 201 and the sub-mirror 202 to a position retracted from a
photographic optical path (mirror up), prior to capturing of an
image in step S509. Upon completion of the mirror up, the
processing proceeds to step S509.
[0056] In step S509, the system control unit 210 causes capturing
of an image by controlling the imaging sensor 209, and stores the
captured image into the internal memory, in association with the
defocus amount detected in step S507. When capturing of the image
is completed, the processing proceeds to step S510. In step S510,
the system control unit 210 moves the main mirror 201 and the
sub-mirror 202 to a position within the photographic optical path
(mirror down). Upon completion of the mirror down, the processing
proceeds to step S511.
[0057] In step S511, the system control unit 210 increments the
counter value n of the counter 214, and then the processing
proceeds to step S512. In step S512, the system control unit 210
determines whether the counter value n has reached the
captured-image count m. If the counter value n has reached the
captured-image count m (Yes in step S512), the processing proceeds
to step S514. If the counter value n has not reached the
captured-image count m (No in step S512), the processing proceeds
to step S513.
[0058] In step S513, the system control unit 210 transmits a
driving instruction to the lens control unit 103, so that the focus
lens is driven toward an infinite-far distance side by a drive
amount corresponding to the bracket interval s described above.
When driving of the focus lens is completed, the processing returns
to step S507. By repeating the processes from step S507 to step
S513, the m number of images varying in focus state by the bracket
interval s are sequentially captured. In the above-described
example, the focus bracket shooting is performed while the focus
lens is driven toward the infinite-far distance side, after the
focus lens is driven toward the closest distance side. However, the
focus bracket shooting may be performed while the focus lens is
driven toward the closest distance side, after the focus lens is
driven toward the infinite-far distance side.
[0059] In step S514, the user selects an image in a desired focus
from among the m number of images varying in focus state by the
bracket interval s. In this process, the display unit 212 displays
the images obtained by the focus bracket shooting. The images may
be displayed one by one, or may be displayed in an array. Further,
the displayed image may be an image subjected to image processing
different from normal processing, to display the focus state
clearly. For example, when a captured image is displayed, the image
is normally subjected to edge enhancement processing to improve
appearance of the image. However, for the image displayed in step
S514, the edge enhancement processing is not performed. The user
operates an operation member (not illustrated), while checking the
images displayed by the display unit 212. The user then selects an
image in a desired focus state, and determines the selected
image.
[0060] Selection of an image is not necessarily required in step
S514. In step S514, for example, when it is difficult to select an
image, no image may be selected for a predetermined time, or the
processing for setting the AF adjustment value may be canceled by
predetermined operation. In such a case (No in step S514), the
processing proceeds to step S516. On the other hand, when an image
is selected (Yes in step S514), the processing proceeds to step
S515.
[0061] In step S515, the system control unit 210 determines the AF
adjustment value, based on the defocus amount associated with the
image selected by the user in step S514. Processing for determining
the AF adjustment value will be described in detail below. Upon
determination of the AF adjustment value, the processing proceeds
to step S516. In step S516, displaying the screen for the focus
bracket shooting adjustment is terminated, which terminates the
calculation of the AF adjustment value in the second adjustment
mode.
[0062] The captured-image count m of the focus bracket shooting may
be a value unique to the imaging apparatus or the lens unit 100,
and may be set depending on the state of an object whenever
necessary. In general, the higher the spatial frequency of an
object is, the easier the determination of an in-focus state is.
Therefore, the number of captured images may be reduced, or the
bracket interval s may be decreased. This also holds true for a
case where object information is edge information, and each
parameter may be set depending on how easy it is to perform
in-focus determination for an object. Each parameter for the focus
bracket shooting may be arbitrarily set by the user.
[0063] Next, a method for determining the AF adjustment value in
the second adjustment mode of the present exemplary embodiment will
be described using FIGS. 6A, 6B, and 6C to FIG. 8. FIGS. 6A, 6B,
and 6C are diagrams illustrating the method for determining the AF
adjustment value in the imaging apparatus of the present exemplary
embodiment. FIG. 6A is a schematic diagram of the focus bracket
shooting described above, and illustrates how images 601 to 609 are
captured while a focus state is shifted. Assume that the
captured-image count m in the bracket shooting is nine. In this
case, by centering a position determined to be in focus based on a
focus detection result obtained in step S502 described above, an
image at this central position as well as preceding four images and
following four images are captured at the bracket intervals s.
[0064] FIG. 6B illustrates each of the focus detection regions and
a focus detection result thereof, in the image 605 at the center (a
fifth image), in a group of the images 601 to 609 obtained in the
focus bracket shooting. The lens position when the image 605 is
captured corresponds to the lens position determined to be in focus
based on the focus detection result obtained in step S502. The
focus detection result illustrated here exemplifies a difference
(in a unit system of the AF adjustment value) from the focus
detection result obtained in step S502 described above. In general,
even in the image 605 at the central position, the focus detection
result of the focus detection region detected in step S507 may not
be zero, due to a lens driving error or a focus detection error in
the focus bracket shooting.
[0065] FIG. 6C illustrates each of the focus detection regions and
a focus detection result thereof in the image 607 selected by the
user, from the group of the images 601 to 609 obtained in the focus
bracket shooting. Here, a region (an image region) 6071 surrounded
with a broken line is used for determination in selecting the image
by the user. For example, in a case where an enlarged image is
displayed when operation for selecting an image is performed by the
user, a region corresponding to this enlarged image can be
determined to be the region 6071.
[0066] FIGS. 7A and 7B each illustrate an example of the AF
adjustment value determined in the second adjustment mode of the
present exemplary embodiment. The method for determining the AF
adjustment value will be described below. FIG. 7A illustrates an
example of the AF adjustment value determined in a first
determination mode, and FIG. 7B illustrates an example of the AF
adjustment value determined in a second determination mode. As
illustrated in FIGS. 7A and 7B, the same AF adjustment value is set
in all the focus detection regions in the first determination mode,
whereas the AF adjustment value is calculated for each of the focus
detection regions in the second determination mode.
[0067] FIG. 8 is a flowchart illustrating the method for
determining the AF adjustment value according to the present
exemplary embodiment. In the present exemplary embodiment, the AF
adjustment value is determined for each of the focus detection
regions, based on the focus detection result obtained in step S507.
In the method for determining the AF adjustment value, the first
determination mode and the second determination mode to be
described below are provided, and the AF adjustment value is
determined in either one of these modes, whichever is selected.
[0068] In step S801, the system control unit 210 reads out the
focus detection result (the defocus amount) of each of the focus
detection regions. The focus detection result is stored in
association with the image (assumed to be the image 607 of FIG. 6C,
here) selected in step S514 described above. When this readout of
the focus detection result is completed, the processing proceeds to
step S802.
[0069] In step S802, the system control unit 210 determines whether
a photographic object is a plane, based on the focus detection
result of each of the focus detection regions. Conceivable examples
of a plane determination scheme include a scheme of determining
that an object is detected by all the focus detection regions from
the same distance, i.e., determining that the object is a plane, if
the defocus amounts of all the focus detection regions in the
selected image 607 are within a predetermined threshold width
(within a threshold).
[0070] In the present exemplary embodiment, if the object is
determined not to be a plane in step S802 (No in step S802), the
first determination mode is adopted, whereas if the object is
determined to be a plane in step S802 (Yes in step S802), the
second determination mode is adopted. However, an operation when
the object is determined not to be a plane is not limited to the
present exemplary embodiment, and may be an operation of cancelling
the second adjustment mode, or performing the bracket shooting
again.
[0071] If the object is determined not to be a plane (No in step
S802), the processing proceeds to steps S804 to S806 that are
processes of the first determination mode. In step S804, the system
control unit 210 detects the image region 6071 used by the user to
determine the focus state, in the image 607 selected in step S514.
Conceivable examples of an image-region detection scheme include a
scheme of detecting, as the image region, a region observed when
image selection operation is performed, e.g., a displayed enlarged
region. Upon detection of the image region, the processing proceeds
to step S805.
[0072] In step S805, the system control unit 210 selects a specific
focus detection region, which is suitable for determination of the
AF adjustment value, from all the focus detection regions. For this
selection, it is conceivable to adopt, for example, a scheme of
selecting a focus detection region 6072 closest to a central part
of the image region 6071, based on the image region 6071 detected
in step S804. Alternatively, a focus detection region that entirely
or at least partially overlaps the image region 6071 may be
displayed as a candidate for selection in a visually recognizable
manner. The user may thereby select a focus detection region to be
used for determination of the AF adjustment value. Upon selection
of the specific focus detection region, the processing proceeds to
step S806.
[0073] In step S806, the system control unit 210 calculates an AF
adjustment value suitable for being uniformly applied to all the
focus detection regions. The AF adjustment value is calculated by
the following method, for example. The defocus amount, which is
stored in association with the specific focus detection region 6072
selected in step S805, is converted into the unit system (1 scale
unit of FIG. 4 is assumed to be 1 unit) of the AF adjustment value.
The AF adjustment value is determined as an offset value that is a
value equivalent to a negative number of the value resulting from
the conversion, so that the value resulting from the conversion
becomes zero. The determined AF adjustment value is adopted for all
the focus detection regions.
[0074] The process in each of steps S802, S804, and S805 is
described to be performed by the system control unit 210. However,
a calculation element for performing each process may be
independently provided.
[0075] On the other hand, if the object is determined to be a plane
in step S802 (Yes in step S802), the processing proceeds to step
S803 that is a process of the second determination mode. In step
S803, based on the focus detection result stored in association
with the image selected in step S514, the system control unit 210
determines AF adjustment values individually for all the focus
detection regions. Here, the object is already determined to be a
plane in step S802 and thus, it can be considered that the obtained
focus detection result indicates that a desired focus state is
achieved in all the focus detection regions. Therefore, for
example, the AF adjustment value is calculated in such a way that,
for each of all the focus detection regions, the defocus amount
associated and stored is converted into the unit system (1 scale
unit of FIG. 4 is assumed to be 1 unit) of the AF adjustment value.
Subsequently, the AF adjustment value is determined as an offset
value that is a value equivalent to a negative number of the value
resulting from the conversion, so that the value resulting from the
conversion becomes zero (so that the focus detection result after
the adjustment becomes zero), in each of the focus detection
regions.
[0076] If the AF adjustment value is determined to be updated in
step S203 in FIG. 2 (Yes in step S203), then in step S204, the AF
adjustment value determined in step S803 or 5806 is stored into the
storage unit 211.
[0077] In the present exemplary embodiment, the defocus amount
detected in step S507 is stored in association with the captured
image. However, the defocus amount may be stored in association
with the captured image, after being converted into the unit system
of the AF adjustment value. In this case, after a value is obtained
by converting the defocus amount detected in each of the focus
detection regions into the unit system of the AF adjustment value,
determination is made as to whether the object is a plane in step
S802, based on whether the obtained value is within a predetermined
threshold width. Further, in step S803 or S806, a value, which is
equivalent to a negative number of the value stored in association
with a target focus detection region, is set as the AF adjustment
value.
[0078] As described above, in the present exemplary embodiment,
there are two modes for determining the AF adjustment value based
on the focus detection result, when the AF adjustment value is set
based on the focus detection result corresponding to the image
selected by the user from among the images obtained in the focus
bracket shooting. These are the first determination mode and the
second determination mode. In the first determination mode, the AF
adjustment value calculated based on the focus detection result in
the specific focus detection region is also applied to the other
focus detection regions. In the second determination mode, the AF
adjustment value is calculated for each of the focus detection
regions, based on the focus detection result. By using these modes,
the AF adjustment value can be readily set in each of the focus
detection regions by simple operation, even when the number of
focus detection regions is large.
[0079] In addition, in the present exemplary embodiment, whether
the object is a plane is determined based on the focus detection
result of each of the focus detection regions, and switching
between the first determination mode and the second determination
mode is performed based on the result of this determination. When
the object is a plane, it is more likely that the same object is
detected in each of the focus detection regions. Therefore, a
highly accurate AF adjustment value can be set for each of the
focus detection regions, by calculating the AF adjustment value in
the second determination mode. On the other hand, when the object
is not a plane, the AF adjustment value is calculated in the
specific focus detection region, which is determined in
consideration of a region to which the user pays attention.
Therefore, a highly accurate AF adjustment value can be set at
least for a focus detection region where the user desires to obtain
focus.
[0080] The preferable exemplary embodiment of the present invention
is described above. However, the present invention is not limited
to the above-described exemplary embodiment, and may be variously
altered or modified within the scope of the gist thereof.
Other Embodiments
[0081] Embodiment(s) of the present invention can also be realized
by a computer of a system or apparatus that reads out and executes
computer executable instructions (e.g., one or more programs)
recorded on a storage medium (which may also be referred to more
fully as a `non-transitory computer-readable storage medium`) to
perform the functions of one or more of the above-described
embodiment(s) and/or that includes one or more circuits (e.g.,
application specific integrated circuit (ASIC)) for performing the
functions of one or more of the above-described embodiment(s), and
by a method performed by the computer of the system or apparatus
by, for example, reading out and executing the computer executable
instructions from the storage medium to perform the functions of
one or more of the above-described embodiment(s) and/or controlling
the one or more circuits to perform the functions of one or more of
the above-described embodiment(s). The computer may comprise one or
more processors (e.g., central processing unit (CPU), micro
processing unit (MPU)) and may include a network of separate
computers or separate processors to read out and execute the
computer executable instructions. The computer executable
instructions may be provided to the computer, for example, from a
network or the storage medium. The storage medium may include, for
example, one or more of a hard disk, a random-access memory (RAM),
a read only memory (ROM), a storage of distributed computing
systems, an optical disk (such as a compact disc (CD), digital
versatile disc (DVD), or Blu-ray Disc (BD).TM.), a flash memory
device, a memory card, and the like.
[0082] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0083] This application claims the benefit of Japanese Patent
Application No. 2014-249677, filed Dec. 10, 2014, which is hereby
incorporated by reference herein in its entirety.
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